Re: Xfade vs. zeroX / HW vs SW (was: dream box)

[Matthias Grob <matthias@grob.org>]

>  >>I think both Kyma and MAX/MSP provide solutions.  This is cool!
>  >>[Sometimes I feel that, if I'm into this "looper religion" thing, 
>then Kyma is like my denomination. :)  That makes the MAX/MSP folks 
>(and Orville users, etc.) like a different denomination; same 
>religion, they just use different words to mean about the same 
>thing!]
>
>>please let me be member of such denomination!
>
>I always thought you were one of the founders!  One of the "fathers of the
>revolution"!!!  Viva la Loop!!!!!!  :)

hmm, I hope it will not turn into revolution, but a peacefull evolution. 
:-)
I contributed with the currage to launch the first dedicated loop unit.
But looping has a much longer story.
So as I undertood your picture, I am the father of the EDP denomination.
And I feel that this dificults my participation / contribution in the 
others, just like in real religions: If you are strong in one tribe 
the members of the others keep distance.
The SW looper specialists may fear that I grab all ideas while in 
fact the oposit is happening lately!

>  >Doesnt the audibility depend on the sound material?
>>Roughly: For percussive sound, the zero crossing is great but for 
>sustained
>  >sound, cross fade is necessary, otherwhise you hear a new attack which 
>can
>  >be about as annoying as a click.
>  >In a future HW solution such fades will be available and probably 
>controllable.
>>The sound material could be analyzed to define characteristic.
>
>Interesting...
>Yes, I think the audibility depends on the sound material, but I 
>would say just
>the opposite!  I.e., I'd use zeroX for sustained sounds.  Here's my 
>experience:
>I wrote a zero-crossing adjuster for Kyma recently.  To test it, I 
>created a
>short loop by humming a continuous tone into the mic and punching 
>in/out.  Sure
>enough, I heard a click at the loop point.  After being 
>zero-adjusted, the click
>completely disappeared.  But perhaps with other sounds, the zeroX would 
>leave
>artifacts.

shure, the click goes away, but couldnt you hear some bump, like as 
if an new such hum tone would start? I had that a lot when editing 
sound files on the Mac.
The only way to get rid of it is a slow Xfade.
The savest place to cut is an attack. I started cutting tape: Roll 
backwards and forewards until you locate the beginning of a note and 
cut there. Shure, the diagonal tape splice also corresponds to a 
cross fade...

So instead of searching for a zero-crossing, you may search for an 
attack. Usually the musician starts a loop with a new note :-)
Cutting at the last zero cross before the attack, you probably dont 
have to care about the end point, because the click will be 
overrolled by the attack, right?

If there is no attack, we need a Xfade, and it can be a long one.

>My zero-crossing adjuster alters the loop length, even if by only a 
>tiny amount.
>It advances the start point and retreats the end point until a 
>zero-crossing
>splice is achieved (with the same signal slope on each side).  The nice 
>thing
>about Xfade is that the loop length can remain EXACTLY the same.  In 
>thinking
>about Alex's original question some more, I think maybe a cross-fade for 
>the
>sub-loop to eliminate clicks but trim the new material with a 
>zero-crossing
>adjustment.

In the worst case, you have to go back almost a phase of say a 33Hz 
note, which is 30ms. If it happens on both ends, its 60... couldnt 
you correct backwards on both ends, so you can do it in real time and 
the error would subtract instead of adding?
With the attack method, you have to correct more, maybe, but usually 
only the entry point. The original loop length can stay untouched, 
unless there is exactly another attack at the end, which is quite 
likely. But in this case you can move the end point to the attack and 
hope that its played more acurately than the musicians foot action, 
so you actually improve loop length.

Ask IVL, they must know a lot about this stuff!


          ---> http://Matthias.Grob.org